xref: /titanic_41/usr/src/lib/libc/i386/fp/fpsetround.c (revision 355b4669e025ff377602b6fc7caaf30dbc218371)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License, Version 1.0 only
6  * (the "License").  You may not use this file except in compliance
7  * with the License.
8  *
9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10  * or http://www.opensolaris.org/os/licensing.
11  * See the License for the specific language governing permissions
12  * and limitations under the License.
13  *
14  * When distributing Covered Code, include this CDDL HEADER in each
15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16  * If applicable, add the following below this CDDL HEADER, with the
17  * fields enclosed by brackets "[]" replaced with your own identifying
18  * information: Portions Copyright [yyyy] [name of copyright owner]
19  *
20  * CDDL HEADER END
21  */
22 /*	Copyright (c) 1990, 1991 UNIX System Laboratories, Inc.	*/
23 /*	Copyright (c) 1988 AT&T	*/
24 /*	  All Rights Reserved  	*/
25 
26 /*
27  * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
28  * Use is subject to license terms.
29  */
30 
31 #pragma ident	"%Z%%M%	%I%	%E% SMI"
32 
33 #pragma weak fpsetround = _fpsetround
34 
35 #include "synonyms.h"
36 #include <ieeefp.h>
37 #include "fp.h"
38 
39 extern int	_sse_hw;
40 extern void	_getmxcsr(int *), _putmxcsr(int);
41 
42 fp_rnd
43 fpsetround(fp_rnd newrnd)
44 {
45 	struct _cw87 cw;
46 	fp_rnd oldrnd;
47 	int	mxcsr;
48 	extern int __flt_rounds;  /* ANSI value for rounding */
49 
50 	newrnd &= 0x3;	/* mask off all ubt last 2 bits */
51 	switch (newrnd) {	/* set ANSI rounding mode */
52 	case FP_RN:	__flt_rounds = 1;
53 			break;
54 	case FP_RM:	__flt_rounds = 3;
55 			break;
56 	case FP_RP:	__flt_rounds = 2;
57 			break;
58 	case FP_RZ:	__flt_rounds = 0;
59 			break;
60 	};
61 	_getcw(&cw);
62 	oldrnd = (fp_rnd)cw.rnd;
63 	cw.rnd = newrnd;
64 	_putcw(cw);
65 	if (_sse_hw) {
66 		_getmxcsr(&mxcsr);
67 		mxcsr = (mxcsr & ~0x6000) | ((int)newrnd << 13);
68 		_putmxcsr(mxcsr);
69 	}
70 	return (oldrnd);
71 }
72